What are the steps of light-dependent reactions of photosynthesis?

1 Answer
Mar 11, 2017

As the name suggests, the light-dependant reaction depends on sunlight to carry out photosynthesis. Here, it traps solar energy and uses it to generate ATP and NADPH.


There are 4 steps to a light-dependant reaction.

First, photosystem II absorbs a photon, which excites an electron causing it to go to the electron acceptor, which means that photosystem II is now missing an electron. It regains the electron from water, producing oxygen. The resulting hydrogen ions remain in the thylakoid space and the oxygen is given off.

From the electron acceptor, the energized electrons are passed on to a series of electron carrying molecules, which forms an electron transport system. As electrons are transferred, the release energy is used to create a hydrogen proton gradient in the tylakoid.

At the same time, photosystem I absorbs light energy - and excited electrons leave the cell and are replaced by electrons coming in from Photosystem II

Electrons received by Photosystem I are used to reduced NADP+ to NADPH for used in light-independant reactions.